Physical Mechanisms of "Shock Cooling" at the Molecular Fluid/Window Interface under Shock Loading

The physical mechanism of "shock cooling" at the molecular fluid/window interface has long puzzled the shock wave physics community. There are three distinct viewpoints explaining the cooling effect at the shock interface: (1) thermal equilibrium between the molecular fluid and the window; (2) extinction effect of the molten optical window; and (3) shock response characteristics of the molecular fluid. This paper comparatively investigates the shock radiative behavior and radiation temperature variation characteristics at the interfaces between the chemically active fluid CHBr3, the inert liquid argon (LAr), and the LiF optical window. Under the same shock pressure, the interface radiation characteristics of the two media exhibit distinct evolution features, indicating that the interface cooling effect is closely related to the fluid medium and its chemical activity. Therefore, the observational results of this paper strongly support that the interface cooling effect is caused by the shock response of the fluid itself, rather than the heat conduction mechanism or the window melting extinction mechanism.